We are about to dig trenches (or rather a man with a large tool is about to) to lay water pipe around the fields. At the same time we are going to lay armoured cable to the field shelter and also to where we hope to build a farrowing shed in the future.

The total length of cable will be around 175 metres, but I need to determine what the expected wattage will be. In terms of what I am expecting to be able to do in either the field shelter or farrowing shed, I might need to boil a kettle (for mixing milk for lambs), and a heat lamp as well in the farrowing shed.

I guess a kettle would use around 2,500 watts and a heat lamp 500, plus perhaps three bulbs at 100 each takes me to 3,300 max in total. Plus 200 spare, and a nice round 3,500.

Based on this I am very much on the margins of what I can do with 10mm cable, so might need 16mm. But that is £140 more

If you're up there, and lambing, might you need a heater for yourself at some point? Perhaps you'll want power tools running to put up shelves, or whatever. I'm prepared to bet that if you go for the cheaper option now, you'll regret it later.

As regards the rating of the power circuit, I'd suggest that *one* 13 amp socket's worth would be plenty useful.
You can easily find small low wattage ("travel"?) kettles, that wouldn't hog the entire output of the line.
A single socket can easily support most power tools and some lighting.

But with the other costs (not least the excavation) as well as the cable itself, and depending on what you want to use *simultaneously*, it may stack up for you that the extra capacity could be very useful and not make too much impact on the overall cost...

If its not a daft question, are not the economics of this such that a small generator would be massively easier and more cost effective anyway?

I have thought about this as well. One of the things that we will need to power will be heat lamps for piglets, and using a generator would become a right royal pain in the **** after a while. Also as we are having the ditches dug for water, it makes sense to chuck electric in as well. The difference between 16mm and 25mm is around £400, and I'm just not convinced that the calc I was given is right.